1. Field of the Invention
The present invention is related to a controlling apparatus for controlling an engine mounted on a vehicle.
2. Description of the Related Art
As one of controlling methods for an engine mounted on a vehicle, torque-based (torque demand) control for controlling the intake air amount, fuel injection amount, ignition timing and so forth with reference to the magnitude of a torque demanded to an engine is available. In the torque-based control, the engine is controlled such that, for example, a target value for an engine torque is calculated based on the acceleration opening, engine speed and so forth and a torque having the target value is acquired. Further, in a vehicle in which an external controlling system such as an automatic transmission, an automatic cruise apparatus or a vehicle stabilization apparatus is mounted, output power demands from the several external controlling systems to the engine are converted into torques and unified by an engine ECU (engine electric controlling unit) and then a torque behavior of the engine is comprehensively controlled.
Conventionally, in the torque-based control, a controlling method is known wherein both of two kinds of controls whose responsibilities to a controlling operation are different from each other, that is, low-response torque control and high-response torque control, are carried out. In the low-response torque control of the former, the torque is controlled, for example, by an intake air amount operation represented by an operation of an electronically controlled throttle. On the other hand, in the high-response torque control of the latter, the torque is controlled, for example, by an ignition timing operation or a fuel injection amount operation. Since not only the responsibilities but also the adjustment widths of the torque are different from each other in the controls, the controls are suitably carried out in response to a running state of the vehicle or an operation state of the engine or the operation amounts by the controls are adjusted cooperatively.
Regarding the torque-based control, Japanese Patent No. 3627464 discloses an engine controlling apparatus wherein a low-response demand torque to be generated in a low-response controlling target and a high-response demand torque to cope with a high-response controlling target are calculated such that an excessive or deficient amount of the former torque is compensated for by the latter torque. In the technique, an intention of the driver of the vehicle, vehicle stability, a driving performance and so forth are satisfied, for example, by compensating for the torque deficiency by a response delay (lag) of an air amount operation by an operation of the fuel injection amount or ignition timing.
In such conventional torque-based control as disclosed in Japanese Patent No. 3627464 mentioned above, high-response torque control is carried out after a torque corresponding to an air response delay of the low-response torque control is estimated. In particular, the high-response demand torque is calculated based on the low-response demand torque estimated and calculated in the low-response torque control. Accordingly, there is a subject that it is difficult to enhance the calculation accuracy of a high-response demand torque unless the calculation accuracy of the low-response demand torque is secured. However, since the low-response demand torque is calculated based on a driver demand torque and an external demand torque and the actual torque is not taken into consideration, there is a limitation to assurance of calculation accuracy.